Method of contracting or compressing,machine for performing the method and articles produced according to the method

ABSTRACT

A process of compacting in which a heating by induction is used and in which for heating the portion of the bar to be compacted, an initial section of the bar is introduced inside an inductive field produced by one or several inductors, and the bar is displaced inside the inductive field in such a way that more and more remote sections from the initial section progressively enter the inductive field. The force of the inductive field and the displacement speed of the bar are regulated in such a way that before coming out of the inductive field every section that is entered into the inductive field has attained the temperature necessary for compacting. Afterwards, an axial pressure for compacting is applied, and the displacement speed of the sections entering into the inductive field is maintained with respect to the axial pressure. The sections of the bar having attained, by means of the compacting, the desired expansion, are finally brought out of the inductive field. Also, apparatus for carrying out the above process and compacted products made by this process.

United States Patent [191 1 3,842,644 Biesmans 1 Oct. 22, 1974 METHOD OF CONTRACTING OR Primary Examiner-Lowell A. Larson COMPRESSING, MACHINE FOR PERFORMING THE METHOD AND ARTICLES PRODUCED ACCORDING TO THE METHOD [75] Inventor: Robert Biesmans, Zichen, Belgium [73] Assignee: Elphiac, Charleroi, Belgium [22] Filed: Apr. 23, 1973 [21] Appl. No.: 353,777

[30] Foreign Application Priority Data Apr. 24, 1972 Belgium 3970 [52] US. Cl 72/342, 72/318, 219/75 [51] Int. Cl B2lj 1/06, B2lj 5/08 [58] Field of Search 72/342, 318; 219/75, 152

[56] References Cited UNITED STATES PATENTS 2,275,763 3/1942 Howard et al. 2l9/7.5 2,480,315 8/1949 Bennett 2l9/7.5 2,791,674 5/1957 Westin et al t 2l9/7.5 2,889,448 6/1959 Hampton i 219/75 3,198,926 8/1965 Melmoth 219/75 Attorney, Agent, or Firm-Raymond A. Robic 5 7] ABSTRACT A process of compacting in which a heating by induction is used and in which for heating the portion of the bar to be compacted, an initial section of the bar is introduced inside an inductive field produced by one or several inductors, and the bar is displaced inside the inductive field in such a way that more and more remote sections from the initial section progressively enter the inductive field. The force of the inductive field and the displacement speed of the bar are regulated in such a way that before coming out of the inductive field every section that is entered into the inductive field has attained the temperature necessary for compacting Afterwards, an axial pressure for compacting is applied, and the displacement speed of the sections entering into the inductive field is maintained with respect to the axial pressure. The sections of the bar having attained, by means of the compacting, the desired expansion, are finally brought out of the inductive field. Also, apparatus for carrying out the above process and compacted products made by this process.

9 Claims, 4 Drawing Figures PAIENIEDomzzmu FIG.I.

FIG.2.

FIG. 3 .12 FULL METHOD OF CONTRACTING OR COMPRESSING, MACHINE FOR PERFORMING THE METHOD AND ARTICLES PRODUCED ACCORDING TO THE METHOD In a known compacting process, a metal bar is progressively heated from an initial portion elevated to a sufficient temperature for compacting by compressing the bar in its axial direction. It has already been suggested to use the heating produced by an induction for such a process but it seems that till now no substantial results have been obtained in this direction.

The present invention relates to a process of compacting in which a heating by induction is used and which is characterized by the fact that for heating the portion of the bar to be compacted, an initial section of the bar is introduced inside an inductive field produced by one or several inductors, that the bar is displaced inside the inductive field in such a way that more and more remote sections from the initial section progressively enter the inductive field, that the force of the inductive field and the displacement speed of the bar are regulated in such a way that before coming out of the inductive field every section that is entered into the inductive field has attained the temperature necessary for compacting, that the compacting axial pressure is applied, that the displacement speed of the sections entering into the inductive field is maintained with respect to the axial pressure, and that the sections of the bar having attained, by means of the compacting, the desired expansion, are brought out of the inductive field.

The invention is explained hereinafter in an exemplary and non-limitative way having reference to the attached drawings, wherein:

FIG. 1 is a schematic view representing the main parts of an apparatus for performing the compacting process according to the invention;

FIG. 2 shows the repartition of the temperature inside a bar;

FIG. 3 is a schematic view representing the main parts of a further embodiment of an apparatus for performing the compacting process according to the present invention;

FIG. 4 shows the repartition of the temperature inside a bar.

Referring now to the drawings, and according to a first embodiment, the process according to the invention is performed in an apparatus comprising a plunger 1, a roller guide 2, an inductor 3 adapted to the diameters of the bar before and after the compacting step and an anvil 4. The inductor 3 is connected to a generator of alternating current 5 the frequency of which is carefully choosen.

A bar 6 is introduced inside the apparatus in the position shown in FIG. 1. In this position, the free end section of the bar 6 is still outside the inductive field of the inductor 3. At this moment, the inductor 3 is put under voltage and the bar 6 moves forward under the action of plunger 1 actuated by an advancing control device, not shown. The section of the free end of the bar is, in this case, the initial section entering inside the inductive field of the inductor 3. The heating power and the advancing speed of the sections of the bar entering inside the inductor are choosen in such a way that before coming out of the inductive field every section that is entered into the inductive field attains in every point the temperature necessary for compacting. Before the section thus heated comes out of the inductive field, the compacting pressure is applied. In this way, the anvil 4 is placed at the beginning of the compacting operation as shown in FIG. I, and due to the dispersion of the inductive field of the inductor 3, slightly inside the inductive field, which is appropriate and beneficial, because the anvil 4 is thus preheated. The end of the heated bar 6 abuts therefore against the anvil 4 and the compacting pressure is established by the thrust on the bar, the forward advancing or displacement of which is maintained by means of the plunger 1 which is actuated by an advancing device, not shown. Once a section has attained the desired expansion, it it pulled out of the inductive field. The pulling out from the inductive field may be obtained, in the extreme, by purely and simply cutting off the feeding current of the inductor. In this way, all the sections come out of the inductive field. If important compaetings are to be obtained, the anvil 4 may be moved away from the inductor in such a way that the compacted sections having attained the desired expansion come out of the inductive field. Conversely, it is also possible to maintain the anvil 4 in its place and to displace the inductor 3. The inductor 3 and the roll guide 2 may, in this case, form a mechanical unit which is displaceable as a unit towards plunger 1. In the latter case, it may be necessary to modify or change the advancing speed of the plunger at the moment when the retreating of the inductor begins, to avoid thereby any appreciable change of the staying period of the heated sections inside the inductive field and therefore of the repartition of the temperature inside the bar.

In order to obtain particularly advantageous results during the compacting step or operation, it is necessary, according to the invention, to suitably choose the parameters of the induction heating. In particular, the average penetration depth of the induced current must be choosen equal to a fraction only of the diameter of the bar to be compacted. The value of the depth of the optimum penetration depends, among other things, of the time during which a section to be compacted of the bar is kept in the inductive field and of the calorific conductibility of the metal. For instance, for steel bars having a diameter between 10 and 25 mm the depth of the penetration may be choosen in the order of onethird of the diameter, if the staying period of a section in the inductor is about 5 to 10 seconds. Thus, the heating by induction, first brings to a forging temperature a layer adjacent to the surface of the bar which communicates the heat to the deeper layers, advancing at the same time in the inductive field. Therefore, there is thus obtained a repartition of the temperature such as schematically shown in FIG. 2. FIG. 2 represents an axial section of the bar 6 in which are shown the lines of surfaces having the same temperature 7, 8, 9 for three different temperatures. Therefore, there exists on the axis of the bar a core which is tougher, such as outlined, for instance, by the surface 8 which makes the process particularly insensitive to lateral deviations and thus permits the obtaining of articles having perfectly compacted parts of great importance such as represented, for example, by the phantom line 10 in the FIG. 1. It is to be noted that the process of the present application results in a particularly advantageous efficiency in the case of articles composed of non ferrous metal such as aluminium, bronze, brass, copper, etc.

According to a further embodiment, the process according to the invention is carried out in an apparatus comprising two roll guides and two inductors l3 and 14, the other component parts of the apparatus not being represented. During a first step, one of the inductors, for instance 14, is actuated and a bar is displaced by a to and fro movement around an initial section, this movement slowly reaching a larger amplitude and finally effecting to a repartition of temperature as shown in FlG. 4 which is symmetrical and, for each of the two inductors 13 and 14 is similar to the repartition according to FIG. 2. When this repartition according to FIG. 4 is reached, bar 15 is brought into the position represented in FlG. 3 and the compacting pressure is applied in the axial direction of the bar, for example, by means of an advancing control device symmetrically acting on two plungers, not shown. The line 16 shows the outline of an example of a compacted article.

In a further embodiment, it is also possible to bring together at the vicinity of the initial section, the two inductors l3 and 14 which produce two inductive fields at each side of the portion to be compacted and, to first heat the region around the initial section. Afterwards, the inductors are separated from each other and brought into a position represented in FIG. 3 and the compacting pressure is applied. The advancing speed of the two portions of the bar is regulated, each portion passing through one of the inductive fields produced by the inductors l3 and 14 in the manner above described for the bar 6 with respect to the inductor 3 of FIG. 1.

From the foregoing description and the drawings it will be apparent that the inductor means comprising the two inductors of FIG. 1 or the pairs of inductors of FIG. 3 constitute an inductor means of varying diameter. That is, portions of the inductor means are farther from the surface of rods 6 or 15 than are other portions thereof. While the drawings show the differently spaced portions as separate inductors, it is to be understood that a single inductor or varying diameter could be employed, and, as used herein, the term source is intended to refer to either separate inductors at different radii or a single inductor of varying diameter from which the induction field can emanage from radially spaced portions or sources.

When for the facility of loading and removing pieces, an open or an opening inductor of the type disclosed in Belgian Pat. No. 702,281, is provided, and the inductive field therefore presents a non rotative symmetry, it is possible, according to the invention, either to communicate to the inductive field a rotating movement either continuous or oscillating around the axis of the bar, or to communicate to the bar a rotating movement around its axis and to maintain the inductive field stationary. An apparatus performing this process may be equipped with a rotation anvil. The rood guide may be replaced by an opening ball sleeve and the plunger may be equipped with a rotating pressure plate. The anvil and the pressure plate are then driven with the same rotating speed by means of a driving device.

I claim:

1. A compacting process wherein a metal bar is progressively heated, by induction heating means, while applying axial pressure thereto to cause radial enlargement of the heated portion of the bar, comprising the steps of:

providing induction heating and constant axial pressure to a first undeformed portion of said bar to produce initial radial enlargement thereof, said induction heating being applied to said bar from an inner source closely adjacent the surface thereof;

relatively moving said bar and inner source, in an axial direction;

inductively heating the portion of said bar thus initially enlarged, from an outer source adjacent said first source but spaced radially outwardly therefrom, while continuing application of said axial pressure, whereby said bar is further enlarged radially; and

relatively moving said bar and outer source in unison with said inner source.

2. The process of claim 1 including the step of positioning an anvil against an end of said rod adjacent said undeformed portion and inductively preheating said anvil from said outer source.

3. The process of claim 1 wherein said inductive heating steps are performed by establishing inductive heating fields of nonrotational symmetry about said bar and relatively rotating said fields and said bar about an axis coinciding with the axis of said bar.

4. The process of claim 1 including the steps of establishing and maintaining the frequency of said induction heating so related to the diameter of said bar that the average penetration depth of the induced currents in said bar is substantially less than the diameter of said bar.

5. The process of claim 1 including further inductively heating said bar from second inner and outer sources axially spaced from said first-named sources with both said outer sources between said inner sources, said moving step being performed by moving said first sources and said second sources axially apart.

6. Apparatus for compacting an elongated metal bar comprising:

means for axially guiding said bar;

at least one movable plunger for applying axial pressure to an end of said bar;

induction heating means having an inner inductor adjacent the surface of said bar and an outer inductor axially adjacent but radially outward therefrom;

said inductors being movable, in unison, axially of said bar.

7. Apparatus as defined in claim 6 including a second movable plunger for applying axial pressure to the other end of said bar;

a second of said induction heating means, both said induction heating means being between said plungers and arranged with their outer inductors between their inner inductors.

8. Apparatus as defined in claim 6 including an anvil against the other end of said bar, said anvil and plunger being rotatable about the axis of said bar, said induction heating means providing an induction field of nonrotational symmetry.

9. Apparatus as defined in claim 6 wherein said induction heating means provides an induction field of non-rotational symmetry and is rotatable about the axis of said bar. 

1. A compacting process wherein a metal bar is progressively heated, by induction heating means, while applying axial pressure thereto to cause radial enlargement of the heated portion of the bar, comprising the steps of: providing induction heating and constant axial pressure to a first undeformed Portion of said bar to produce initial radial enlargement thereof, said induction heating being applied to said bar from an inner source closely adjacent the surface thereof; relatively moving said bar and inner source, in an axial direction; inductively heating the portion of said bar thus initially enlarged, from an outer source adjacent said first source but spaced radially outwardly therefrom, while continuing application of said axial pressure, whereby said bar is further enlarged radially; and relatively moving said bar and outer source in unison with said inner source.
 2. The process of claim 1 including the step of positioning an anvil against an end of said rod adjacent said undeformed portion and inductively preheating said anvil from said outer source.
 3. The process of claim 1 wherein said inductive heating steps are performed by establishing inductive heating fields of nonrotational symmetry about said bar and relatively rotating said fields and said bar about an axis coinciding with the axis of said bar.
 4. The process of claim 1 including the steps of establishing and maintaining the frequency of said induction heating so related to the diameter of said bar that the average penetration depth of the induced currents in said bar is substantially less than the diameter of said bar.
 5. The process of claim 1 including further inductively heating said bar from second inner and outer sources axially spaced from said first-named sources with both said outer sources between said inner sources, said moving step being performed by moving said first sources and said second sources axially apart.
 6. Apparatus for compacting an elongated metal bar comprising: means for axially guiding said bar; at least one movable plunger for applying axial pressure to an end of said bar; induction heating means having an inner inductor adjacent the surface of said bar and an outer inductor axially adjacent but radially outward therefrom; said inductors being movable, in unison, axially of said bar.
 7. Apparatus as defined in claim 6 including a second movable plunger for applying axial pressure to the other end of said bar; a second of said induction heating means, both said induction heating means being between said plungers and arranged with their outer inductors between their inner inductors.
 8. Apparatus as defined in claim 6 including an anvil against the other end of said bar, said anvil and plunger being rotatable about the axis of said bar, said induction heating means providing an induction field of non-rotational symmetry.
 9. Apparatus as defined in claim 6 wherein said induction heating means provides an induction field of non-rotational symmetry and is rotatable about the axis of said bar. 